The proteasome is an intracellular protease that is responsible for a significant amount of proteolysis, including the degradation of oxidized proteins and a large number of established short-lived proteins lacking oxidative modifications. Increasing evidence suggests that inhibition of the proteasome-proteolytic pathway occurs as a part of normal aging, with inhibition of proteasome function likely contributing to numerous age-related alterations in the proteome, including age-related increases in oxidized protein. However, the lack of a rigorous biochemical and proteomic analysis has made such estimations largely hypothetical and theoretical. Dietary restriction (DR) is the only known manipulation to consistently and reliably increase average and maximal lifespan in mammals. Numerous studies have demonstrated that DR can ameliorate age-related increases in oxidized protein, and suppress a variety of age-related alterations to the proteome. Data from our laboratory demonstrates that DR ameliorates age-related impairments in proteasome function, with the preservation of proteasome function possibly contributing to the beneficial effects of DR on the proteome. The focus of this proposal is to utilize rigorous proteomic and biochemical analysis to test the hypothesis that DR ameliorates age-related impairments in proteasome function as the result of its direct effects on the proteasome complex, with the preservation of proteasome activity contributing to DR-induced effects on the proteome (oxidized and non-oxidized proteins) during normal aging. The specific aims for testing this hypothesis are as follows: (1) To determine the effects of DR on proteasome subunit expression, proteasome biogenesis, proteasome composition, and proteasome oxidation;(2) To determine the effects of DR on the individual peptidase activities and protein degrading capabilities of the proteasome;(3) To determine the cell-type specific effects of impaired proteasome function on the proteome, including protein oxidation, in primary CNS cell cultures in vitro;(4) To determine if proteins which exhibit altered expression or increased oxidation following proteasome inhibition in vitro, exhibit similar changes during aging in vivo;(5) To determine if DR ameliorates alterations in the proteome, including increases in oxidized protein, observed during aging in vivo and following proteasome inhibition in vitro.